From Mad Gender Science!

Fulvestrant is a selective estrogen receptor degrader and downregulator[1]. It binds to estrogen receptors and causes them to be degraded, i.e., broken down into their constituent amino acids.

The medication inhibits estradiol binding in the breast at a much higher level than tamoxifen[2], is a complete (not partial) ER antagonist due to disrupting AF1 and AF2 sites that fuel breast and breast cancer growth, and also destroys estrogen receptors.


  1. Fulvestrant. Drugbank. https://www.drugbank.ca/drugs/DB00947
  2. Osborne, Wakeling, Nicholson. Fulvestrant: an oestrogen receptor antagonist with a novel mechanism of action. Published online 2004 Mar 5. Available from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2750773/